Complaint
Complaints are expressions of "displeasure or annoyance" in response to an action that is seen by the speaker as unfavorable. Here's one of complaining dialogue:

Mr Ryefield: waiter!
Waiter: Is everything all right, sir?
Mr Ryefield: Not exactly. This steak is raw. I asked for it well done! And it´s rather cold.
Waiter: I do apologise, sir. Would you like it cooked a little more?
Mr Ryefield: Please.
Waiter: Would you like something else while you´re waiting?
Mr Ryefield: No, thank you. But tell them to hurry.

Making a Complaint:
Here are useful expressions you can use when complaining:

Excuse me, there seems to be something wrong with…

Excuse me, there appears to be something wrong…

I wonder if you could help me…..

Responding to complaints
Accepting a Complaint:

Oh, I’m sorry about that.

I can’t tell you how sorry I am

I wish it never happened

Delaying a Complaint

I suggest you leave it with us and we’ll see what can be done.

I suggest you leave it with us and we’ll see what we can do.

I’m afraid the manager/boss isn't in at the moment. Could you call later?

Rejecting a Complaint

Sorry there is nothing we can do about it.

I'm afraid, there isn't much we can do about it.

We are sorry but the food is just alright.

Giving Instruction
Giving instruction is an expression that is used in order that order that other person does what we instruct or request, or giving imperative to other people for to do or not to do something, Giving instruction sometimes called comparative/prohibition. The tense used in giving instruction is simple present.

There are two parts to giving instructions. What we call Sequencers and then the actions.
sequencers are the words that help order your instructions. It is like the 1, 2, 3, 4 of your actions.
The most common are First(ly), ...Then, ...Next, ...After that, ...Finally, ...

> Sequencing

Before you begin, (you should . . .)

The first thing you do is . . . .

I would start by . . .

The best place to begin is . . .

To begin with,

> Starting out

After that,

The next step is to . . .

The next thing you do is . . .

Once you've done that, then . . .

When you finish that, then . . .

> Continuing

The last step is . . .

The last thing you do is . . .

In the end,

When you've finished,

When you've completed all the steps

> Finishing
Instructions
do one of three things.
1) Tell people what is necessary.
2) what is wrong.
3) what is not necessary.